Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

8. Elimination Reactions

Cumulative Substitution/Elimination

Organic Chemistry

8. Elimination Reactions

Cumulative Substitution/Elimination

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Problem 39d

Textbook Question

Would you expect the following bases to favor E1 or E2 elimination?
(d) H₂O

Verified step by step guidance

Step 1: Begin by understanding the difference between E1 and E2 elimination mechanisms. E1 is a two-step process involving the formation of a carbocation intermediate, while E2 is a one-step process where the base abstracts a proton as the leaving group departs simultaneously.

Step 2: Analyze the nature of the base provided in the problem. H2O (water) is a weak base and also a polar protic solvent. Weak bases typically favor E1 elimination because they are not strong enough to efficiently abstract a proton in a concerted E2 mechanism.

Step 3: Consider the role of the solvent. Polar protic solvents, like H2O, stabilize carbocation intermediates through hydrogen bonding, which makes the E1 mechanism more favorable.

Step 4: Evaluate the substrate. If the substrate can form a stable carbocation (e.g., tertiary or secondary alkyl halides), this further supports the likelihood of an E1 mechanism over E2 when H2O is the base.

Step 5: Conclude that H2O, being a weak base and polar protic solvent, would favor the E1 elimination mechanism under typical conditions, especially if the substrate can form a stable carbocation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

E1 and E2 Mechanisms

E1 (unimolecular elimination) and E2 (bimolecular elimination) are two distinct mechanisms for elimination reactions in organic chemistry. E1 involves a two-step process where the leaving group departs first, forming a carbocation, followed by deprotonation to form the alkene. In contrast, E2 is a one-step mechanism where the base abstracts a proton while the leaving group exits simultaneously, leading to the formation of the alkene.

Role of the Base

The strength and structure of the base play a crucial role in determining whether an E1 or E2 mechanism will dominate. Strong bases typically favor E2 reactions due to their ability to abstract protons quickly, while weak bases, like water, are more likely to participate in E1 reactions, as they do not effectively promote simultaneous proton abstraction and leaving group departure.

Solvent Effects

The choice of solvent can significantly influence the pathway of elimination reactions. Polar protic solvents, such as water, stabilize carbocations and can facilitate E1 mechanisms by solvating the leaving group. In contrast, polar aprotic solvents favor E2 mechanisms by enhancing the nucleophilicity of the base, making the solvent's nature an important factor in predicting the reaction outcome.

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